I started asking questions about ventilation to respected herp vets (Benoit and Rossi). I was told that there could not be enough only too little. The next expected question was how much is too little? I was told with no water dish and dry substrate in 2 hours the tub should be the same as the room. I use a fairly large water bowl (5 inch) and coco coir that adds about 10% RH to over the room. My room with no humidifier is between 15% and 30% RH. The tubs sit at 25 and 40%. 40% is at the lowest of ok but 35% is too low. I simply humidify the room it is the easiest option. No concerns about low ventilation related health issues, and no issues with shedding.

I believe you and I believe you have a correct balance. I also know it is hard won and there have been people here whom have decided that no ventilation was fine and ended up with a whole collection having RI. I simply cannot believe it is not at least in part related. I can't say exactly how little is too little, I always suggest more than less.

The Barkers of VPI state,

"They (ball pythons) do not tolerate poor ventilation without suffering the consequences. Keeping ball pythons in high humidity without good ventilation is courting problems of health and maintenance. This is one area in which the herp maxim, "It's best to err on the side of dry," is definitely applicable.

Ball Pythons Barker and Barker 2006 pp. 41